1. Field of the Invention
The present invention relates to a photoelectric converter such as an image sensor used in an image information processing apparatus such as a copying apparatus, facsimile apparatus or a video camera, or an AE/AF sensor of an automatic exposure and/or automatic focusing device of a camera.
2. Related Background Art
Recent advances in electronic technology have brought about attempts at designing higher performance products, including cameras, copying machines and facsimile machines.
For example, in a single reflex type camera, almost all products are presently equipped with the automatic exposure (AE) function and the automatic focusing (AF) function.
In the AE function, an absolute light intensity of an entire area in one frame corresponding to an image pickup area or one of divisional areas of one frame area is measured to automatically control the exposure or shutter speed. On the other hand, in the AF function, a distance to an object is calculated by a correlation function of an object pattern to automatically control lens position.
Thus, in order to enhance the precision, it is necessary to further subdivide the image pickup area.
Because the image pickup areas and the post-processing are different between the AE and the AF, it is necessary to use separate photo-electric converters (sensors). While various improvements have been made in the individual products to reduce the cost, a significant impact has not been achieve.
In the photometry sensor used for the AE function, when a light intensity of an entire area is to be detected, signals of respective areas are amplified by logarithmic amplifiers and output signals thereof are multiplexed.
In the distance measurement sensor used for the AF function, emitters of phototransistors for the respective photo-sensing areas are connected in, common and a peak signal is measured. It is difficult to measure an absolute light intensity of the entire photo-sensing area by this and so it is not used for the AE function.
A typical example of the photometry sensor is described in detail in U.S. Pat. No. 5,115,124 and a typical example of the distance measurement sensor is described in detail in U.S. Pat. No. 4,751,559.
In the former method, the signal processing in the succeeding stage and the drive of the decoder to multiplex the signals are complex, and the latter method is not suitable for the AE function.